gets the if coded, but test fail die to instruction being a graph now

lib/ast/if_expression.rb

@@ -3,12 +3,27 @@ module Ast
 #    attr_reader  :cond, :if_true, :if_false
     def compile frame , method
       is = cond.compile(frame , method)
-#      is.is_false(frame,method)
+      #      is.is_false(frame,method)
+      # TODO should/will use different branches for different conditions. 
+      branch = Virtual::ImplicitBranch.new
+      method.add branch
       last = is
       if_true.each do |part|
         last = part.compile(frame,method )
         raise part.inspect if last.nil?
       end
+      label = Virtual::Label.new
+      method.add label
+      branch.swap
+      method.current = branch
+      if_false.each do |part|
+        last = part.compile(frame,method )
+        raise part.inspect if last.nil?
+      end
+      method.add label
+      branch.swap
+      method.current = label
+      #TODO should return the union of the true and false types
       last
     end
     def old

lib/virtual/instruction.rb

@@ -25,13 +25,44 @@ module Virtual
   # it is indeed the first instruction as just this instruction is the smallest possible programm for the machine.
   # As such it is the next instruction for any first instruction that we generate.
   class Halt < Instruction    
-    
   end
 
   # following classes are stubs. currently in brainstorming mode, so anything may change anytime
-  class MethodDefinitionEnter < Instruction
+  class MethodEnter < Instruction
   end
 
+  #resolves to nothing, but allows forward definition
+  class Label < Instruction
+  end
+
+  # the next instruction represents the true branch and the other is the .... other
+  # could have been the false, but false is a keyword and is asymetric to next anyway
+  # this is an abstract base class (though no measures are taken to prevent instantiation) and derived
+  # class names indicate the actual test
+  class Branch < Instruction
+    def initialize nex = nil , other = nil
+      super(nex)
+      @other = other
+    end
+    attr_reader :other
+    def attributes
+      [:other] + super
+    end
+    # so code can be "poured in" in the same way as normal, we swap the braches around in after the true condition
+    # and swap them back after
+    def swap
+      tmp = @other
+      @other = @next
+      @next = tmp
+    end
+  end
+
+  # implicit means there is no explcit test involved.
+  # normal ruby rules are false and nil are false, EVERYTHING else is true (and that includes 0)
+  class ImplicitBranch < Branch
+  end
+
+  # A note: future branch conditions include OverflowBranch and other non-c 
   class FrameGet < Instruction
     def initialize name , nex = nil
       super(nex)